I build my own frames ( fillet brazed steel) and am going to build my first touring frame, i'm looking for ideas for tube sets that other builders like to use, this is a small frame ( i'm 5'6" 125 lbs) thanks
My experience with frame building is limited to one a long time ago, so don't put too much faith in my comments. Consider them as food for thought.
Given how light you are and the fact that it will be a small frame, I would be inclined to build pretty light unless you pack especially heavy. If you carry a reasonable load of 30 pounds or less you will still be loaded lighter than most riders with no gear at all. Even if you packed 50 pounds of gear you would still be more lightly loaded than a lot of unladen riders.
Personally, I'd build light and pack light. If you want to use longer chain stays and more relaxed angles then go for it, but at your weight I'd tour on something closer to a road race bike than a touring bike, but that is just my preference. Actually I do that even though I am 70 pounds heavier than you.